fs/squashfs/decompressor_multi.c

   1 /*
   2  *  Copyright (c) 2013
   3  *  Minchan Kim <minchan@kernel.org>
   4  *
   5  *  This work is licensed under the terms of the GNU GPL, version 2. See
   6  *  the COPYING file in the top-level directory.
   7  */
   8 #include <linux/types.h>
   9 #include <linux/mutex.h>
  10 #include <linux/slab.h>
  11 #include <linux/buffer_head.h>
  12 #include <linux/sched.h>
  13 #include <linux/wait.h>
  14 #include <linux/cpumask.h>
  15
  16 #include "squashfs_fs.h"
  17 #include "squashfs_fs_sb.h"
  18 #include "decompressor.h"
  19 #include "squashfs.h"
  20
  21 /*
  22  * This file implements multi-threaded decompression in the
  23  * decompressor framework
  24  */
  25
  26
  27 /*
  28  * The reason that multiply two is that a CPU can request new I/O
  29  * while it is waiting previous request.
  30  */
  31 #define MAX_DECOMPRESSOR        (num_online_cpus() * 2)
  32
  33
  34 int squashfs_max_decompressors(void)
  35 {
  36         return MAX_DECOMPRESSOR;
  37 }
  38
  39
  40 struct squashfs_stream {
  41         void                    *comp_opts;
  42         struct list_head        strm_list;
  43         struct mutex            mutex;
  44         int                     avail_decomp;
  45         wait_queue_head_t       wait;
  46 };
  47
  48
  49 struct decomp_stream {
  50         void *stream;
  51         struct list_head list;
  52 };
  53
  54
  55 static void put_decomp_stream(struct decomp_stream *decomp_strm,
  56                                 struct squashfs_stream *stream)
  57 {
  58         mutex_lock(&stream->mutex);
  59         list_add(&decomp_strm->list, &stream->strm_list);
  60         mutex_unlock(&stream->mutex);
  61         wake_up(&stream->wait);
  62 }
  63
  64 void *squashfs_decompressor_create(struct squashfs_sb_info *msblk,
  65                                 void *comp_opts)
  66 {
  67         struct squashfs_stream *stream;
  68         struct decomp_stream *decomp_strm = NULL;
  69         int err = -ENOMEM;
  70
  71         stream = kzalloc(sizeof(*stream), GFP_KERNEL);
  72         if (!stream)
  73                 goto out;
  74
  75         stream->comp_opts = comp_opts;
  76         mutex_init(&stream->mutex);
  77         INIT_LIST_HEAD(&stream->strm_list);
  78         init_waitqueue_head(&stream->wait);
  79
  80         /*
  81          * We should have a decompressor at least as default
  82          * so if we fail to allocate new decompressor dynamically,
  83          * we could always fall back to default decompressor and
  84          * file system works.
  85          */
  86         decomp_strm = kmalloc(sizeof(*decomp_strm), GFP_KERNEL);
  87         if (!decomp_strm)
  88                 goto out;
  89
  90         decomp_strm->stream = msblk->decompressor->init(msblk,
  91                                                 stream->comp_opts);
  92         if (IS_ERR(decomp_strm->stream)) {
  93                 err = PTR_ERR(decomp_strm->stream);
  94                 goto out;
  95         }
  96
  97         list_add(&decomp_strm->list, &stream->strm_list);
  98         stream->avail_decomp = 1;
  99         return stream;
 100
 101 out:
 102         kfree(decomp_strm);
 103         kfree(stream);
 104         return ERR_PTR(err);
 105 }
 106
 107
 108 void squashfs_decompressor_destroy(struct squashfs_sb_info *msblk)
 109 {
 110         struct squashfs_stream *stream = msblk->stream;
 111         if (stream) {
 112                 struct decomp_stream *decomp_strm;
 113
 114                 while (!list_empty(&stream->strm_list)) {
 115                         decomp_strm = list_entry(stream->strm_list.prev,
 116                                                 struct decomp_stream, list);
 117                         list_del(&decomp_strm->list);
 118                         msblk->decompressor->free(decomp_strm->stream);
 119                         kfree(decomp_strm);
 120                         stream->avail_decomp--;
 121                 }
 122                 WARN_ON(stream->avail_decomp);
 123                 kfree(stream->comp_opts);
 124                 kfree(stream);
 125         }
 126 }
 127
 128
 129 static struct decomp_stream *get_decomp_stream(struct squashfs_sb_info *msblk,
 130                                         struct squashfs_stream *stream)
 131 {
 132         struct decomp_stream *decomp_strm;
 133
 134         while (1) {
 135                 mutex_lock(&stream->mutex);
 136
 137                 /* There is available decomp_stream */
 138                 if (!list_empty(&stream->strm_list)) {
 139                         decomp_strm = list_entry(stream->strm_list.prev,
 140                                 struct decomp_stream, list);
 141                         list_del(&decomp_strm->list);
 142                         mutex_unlock(&stream->mutex);
 143                         break;
 144                 }
 145
 146                 /*
 147                  * If there is no available decomp and already full,
 148                  * let's wait for releasing decomp from other users.
 149                  */
 150                 if (stream->avail_decomp >= MAX_DECOMPRESSOR)
 151                         goto wait;
 152
 153                 /* Let's allocate new decomp */
 154                 decomp_strm = kmalloc(sizeof(*decomp_strm), GFP_KERNEL);
 155                 if (!decomp_strm)
 156                         goto wait;
 157
 158                 decomp_strm->stream = msblk->decompressor->init(msblk,
 159                                                 stream->comp_opts);
 160                 if (IS_ERR(decomp_strm->stream)) {
 161                         kfree(decomp_strm);
 162                         goto wait;
 163                 }
 164
 165                 stream->avail_decomp++;
 166                 WARN_ON(stream->avail_decomp > MAX_DECOMPRESSOR);
 167
 168                 mutex_unlock(&stream->mutex);
 169                 break;
 170 wait:
 171                 /*
 172                  * If system memory is tough, let's for other's
 173                  * releasing instead of hurting VM because it could
 174                  * make page cache thrashing.
 175                  */
 176                 mutex_unlock(&stream->mutex);
 177                 wait_event(stream->wait,
 178                         !list_empty(&stream->strm_list));
 179         }
 180
 181         return decomp_strm;
 182 }
 183
 184
 185 int squashfs_decompress(struct squashfs_sb_info *msblk, struct buffer_head **bh,
 186         int b, int offset, int length, struct squashfs_page_actor *output)
 187 {
 188         int res;
 189         struct squashfs_stream *stream = msblk->stream;
 190         struct decomp_stream *decomp_stream = get_decomp_stream(msblk, stream);
 191         res = msblk->decompressor->decompress(msblk, decomp_stream->stream,
 192                 bh, b, offset, length, output);
 193         put_decomp_stream(decomp_stream, stream);
 194         if (res < 0)
 195                 ERROR("%s decompression failed, data probably corrupt\n",
 196                         msblk->decompressor->name);
 197         return res;
 198 }